Journal of the Japan Society of Erosion Control Engineering, Vol.56,No.3,2003

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Development on the numerical model of the red sediment outflow in a catchment and its simulation

Noriyuki MINAMI, Wataru SAKURAI, Takashi YAMADA, Hideaki KIKUCHI, Yoshiiku MUSASHI

Abstract
The aim at this research is to develop a numerical simulation method that can predict the red sediment outflow from pineapple fields to river mouths in Okinawa river basins where red sediment outflow causes serious turbid water problems. The red sediment outflow model was developed under various conditions: expanding the ratio of field surface cover by pineapple leaf reduces the area of sediment yielding, erosion occurrence due to the shear force by the surface flow on the over]saturated surface of the pineapple field, and sediment movement as suspended load. This model was employed to develop a numerical simulation method based on a two]dimensional analysis for the riverbed variation, and can predict the red sediment outflow from the pineapple fields to rivers. Results of a numerical simulation of the Saan River catchment in Higashi Village accurately reproduced the red sediment hydrograph.

Key words:Okinawa, erosion of over]saturated surface of the pineapple field, red sediment outflow,numerical simulation model